U.S. patent number 8,895,292 [Application Number 12/421,252] was granted by the patent office on 2014-11-25 for microfluidic chip devices and their use.
This patent grant is currently assigned to Valtion Teknillinen Tutkimuskeskus. The grantee listed for this patent is Ari Hokkanen, Kari Kataja, Kai Kolari, Jan Rautio, Stella Rovio, Reetta Satokari, Heli Siren, Hans Soderlund, Ingmar Stuns. Invention is credited to Ari Hokkanen, Kari Kataja, Kai Kolari, Jan Rautio, Stella Rovio, Reetta Satokari, Heli Siren, Hans Soderlund, Ingmar Stuns.
United States Patent |
8,895,292 |
Soderlund , et al. |
November 25, 2014 |
**Please see images for:
( Certificate of Correction ) ** |
Microfluidic chip devices and their use
Abstract
A microfluidic chip device (MCD) and its use for performing
miniaturized assays on magnetic microbeads (MMs) are described. The
MCD is particularly useful for carrying out miniaturized transcript
analysis by aiding affinity capturing (TRAC) assays, including PCR.
The MCD comprises at least one reaction chamber with sealable
liquid connections and at least one fluidic pillar filter in each
chamber. The fluidic pillar filter comprises rods with spacings
allowing MMs to pass. The sealable liquid connections feed liquid
to the reaction chamber, wherein air bubbles are removed. The
liquid stream contacts the MMs, which are manipulated with a
magnetic rod. The liquid connections enable trapping of the MMs
behind the pillar filters or in the channel, while the liquid is
changed.
Inventors: |
Soderlund; Hans (Espoo,
FI), Hokkanen; Ari (Espoo, FI), Kataja;
Kari (Espoo, FI), Stuns; Ingmar (Espoo,
FI), Kolari; Kai (Espoo, FI), Siren;
Heli (Espoo, FI), Rovio; Stella (Espoo,
FI), Satokari; Reetta (Espoo, FI), Rautio;
Jan (Espoo, FI) |
Applicant: |
Name |
City |
State |
Country |
Type |
Soderlund; Hans
Hokkanen; Ari
Kataja; Kari
Stuns; Ingmar
Kolari; Kai
Siren; Heli
Rovio; Stella
Satokari; Reetta
Rautio; Jan |
Espoo
Espoo
Espoo
Espoo
Espoo
Espoo
Espoo
Espoo
Espoo |
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A |
FI
FI
FI
FI
FI
FI
FI
FI
FI |
|
|
Assignee: |
Valtion Teknillinen
Tutkimuskeskus (Espoo, FI)
|
Family
ID: |
39385927 |
Appl.
No.: |
12/421,252 |
Filed: |
April 9, 2009 |
Prior Publication Data
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|
|
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Document
Identifier |
Publication Date |
|
US 20090269767 A1 |
Oct 29, 2009 |
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Foreign Application Priority Data
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Apr 10, 2008 [FI] |
|
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20085299 |
|
Current U.S.
Class: |
435/287.1;
435/6.1; 422/68.1; 422/501 |
Current CPC
Class: |
G01N
33/54366 (20130101); B01L 3/50273 (20130101); G01N
33/54326 (20130101); B01L 3/502761 (20130101); B01L
2400/086 (20130101); B01L 2200/0652 (20130101); B01L
2200/0668 (20130101); B01L 2200/0684 (20130101); B01L
2300/0681 (20130101); B01L 2200/10 (20130101); B01L
2300/16 (20130101); B01L 2300/087 (20130101); B01L
2300/0636 (20130101); B01L 2400/088 (20130101); G01N
35/0098 (20130101); B01L 2200/027 (20130101) |
Current International
Class: |
C12M
1/34 (20060101); G01N 33/48 (20060101); C12Q
1/68 (20060101) |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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1 792 655 |
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Jun 2007 |
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EP |
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WO 0185341 |
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Nov 2001 |
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WO |
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WO 02093125 |
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Nov 2002 |
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WO |
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WO 2006/032044 |
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Mar 2006 |
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WO |
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WO 2007/000401 |
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Jan 2007 |
|
WO |
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WO 2007035498 |
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Mar 2007 |
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WO |
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WO 2008/007270 |
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Jan 2008 |
|
WO |
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WO 2008/094198 |
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Aug 2008 |
|
WO |
|
Other References
Pamme et al "On-chip free-flow magnetophoresis: Continuous flow
separation of magnetic particles and agglomerates" Anal. Chem,
2004, 76: 7250-7256. cited by examiner .
Liu Y-J et al.; "A micropillar-integrated smart microfluidic device
for specific capture and sorting of cells"; Electrophoresis; Nov.
2007; vol. 28; p. 4713-4722. cited by applicant .
Wang Y-J et al.; Study of a novel microfluidic DNA extraction chip;
Weinadianzi Jishu; Oct. 2007; vol. 44; No. 9; p. 853-856, 867
(abstract). cited by applicant.
|
Primary Examiner: Forman; Betty
Attorney, Agent or Firm: Arent Fox LLP
Claims
What is claimed:
1. A microfluidic chip device, comprising a microfluidic channel
system comprising at least two reaction chambers interconnected
with a channel having three or more liquid connections, the channel
comprising sealable fluidic connections on both sides of the at
least two reaction chambers, wherein the sealable fluidic
connections act as inlets and/or outlets for a liquid stream,
magnetic microbeads provided within at least one reaction chamber
of the microfluidic channel system, wherein each reaction chamber
comprises at least one microfluidic pillar filter within the
reaction chamber, wherein the microfluidic pillar filter comprises
pillar rods having interspaces sized to allow the magnetic
microbeads to pass the interspaces one by one, and wherein the at
least one microfluidic pillar filter filters bubbles formed in the
liquid streams, and disintegrates clusters of magnetic
microbeads.
2. The microfluidic chip device according to claim 1, wherein the
microfluidic channel system further comprises equipment selected
from the group consisting of magnetic equipment, electric
equipment, optical equipment, and combinations thereof.
3. The microfluidic chip device according to claim 2, wherein the
equipment is integrated or externally connected.
4. The microfluidic chip device according to claim 3, wherein the
equipment is used for carrying out techniques selected from the
group consisting of isolation, purification, concentration, binding
assays, PCR, and reduction of background.
5. The microfluidic chip device according to claim 2, wherein the
equipment is magnetic equipment, and the magnetic equipment
comprises one or more externally manipulatable magnetic rods.
6. The microfluidic chip device according to claim 2, wherein the
equipment is electric equipment, and the electric equipment
comprises electric connections selected from the group consisting
of electric needles and electric thin film elements.
7. The microfluidic chip device according to claim 6, wherein the
electric thin film elements are selected from the group consisting
of heating elements, temperature measurement elements, high voltage
elements, conductivity measurement elements, and combinations
thereof.
8. The microfluidic chip device according to claim 1, wherein the
microfluidic channel system further comprises integrated or
externally connected fractionation and separation equipment.
9. The microfluidic chip device according to claim 8, wherein the
fractionation and separation equipment comprises straight or looped
channels for carrying out capillary electrophoresis with or without
isatachophoresis pre-separation or mass spectrometry.
10. The microfluidic chip device according to claim 1, wherein the
microfluidic channel system further comprises integrated or
externally connected detector equipment selected from the group
consisting of equipment for measuring fluorescence, equipment for
measuring UV/IS absorption, equipment for measuring IR, equipment
for measuring conductivity, equipment for measuring refraction
index, and a mass spectrometer.
11. The microfluidic chip device according to claim 1, wherein the
sealable fluidic connections are fluidic connectors having seals
preventing leakage.
12. The microfluidic chip device according to claim 1, wherein the
microfluidic chip device comprises two layers.
13. The microfluidic chip device according to claim 12, wherein the
microfluidic chip device comprises a bottom layer and a top layer
with holes.
14. The microfluidic chip device according to claim 13, wherein the
microfluidic chip device is contacted to external detector
equipment through a measurement interface, and a steering plate
with steering rods fitting in the holes on the microfluidic chip
device.
15. The microfluidic chip device according to claim 2, wherein the
microfluidic chip device and external equipment are placed on a
docking platform.
Description
RELATED APPLICATION INFORMATION
This application claims priority to Finnish Patent Application No.
20085299, filed on Apr. 10, 2008. This foreign priority application
is incorporated herein by reference in its entirety.
TECHNICAL FIELD OF THE INVENTION
The present invention is related to microfluidics, particularly to
microfluidic chip devices for performing binding assays, including
PCR-reactions, with one or a plurality of binding partners using
several adsorption and desorption steps on magnetic microbeads.
Also disclosed are methods for manipulating magnetic microbeads in
said microfluidic chip devices as well as the use of said
microfluidic chip device and method for manipulating magnetic
microbeads for increasing the sensitivity and efficacy of
micro-scale binding assays performed on magnetic microbeads.
BACKGROUND OF THE INVENTION
Microfluidics is a technology dealing with diminutive amounts of
flowing liquid solutions, which are fed through microchannels
placed on microchips. Said technology is rapidly emerging as a new,
more sensitive alternative to the powerful oligomer-chip
technology.
The microfluidic systems have been used for purification,
separation or sequencing and include methods such as microcapillary
electrophoresis, packed bed immuno- or enzyme-reactors (U.S. Publ.
Appl. No. 2002/0023841, U.S. Publ. Appl. No. 2004/0094419, PCT
Publ. Appl. No. WO 2005/09481, PCT Publ. Appl. No. WO 03/099438,
and PCT Publ. Appl. No. WO 2007/035498). Microfludic devices with
pillar filters are described in PCT Publ. Appl. No. WO 2008/024070,
PCT Publ. Appl. No. WO 01/85341, PCT Publ. Appl. No. WO
2007/098027, PCT Publ. Appl. No. WO 99/09042, and PCT Publ. Appl.
No. WO 02/093125, as well as in Liu et al., Electrophoresis,
November 2007, vol. 28, 4173-4722), but automation and
miniaturizing of binding assays are also suggested. Conventional
binding assays usually take place in solution and include reactions
between binding partners and their counterparts which together form
binding pairs. Examples of binding pairs are antibodies and
antigens or complementary probe and target sequences. In a typical
binding assay the binding partners of the binding pairs are
alternating between solid and liquid phases with intermediate
purification and extraction stages, which are performed on
microbeads.
In the patent literature, few of the problems encountered in
miniaturizing conventional binding assays are discussed, but it is
evident that magnetic particles, which are very convenient in
macroscale conventional binding assays, are not quite as easy to
manipulate when used in microfluidic applications. This is probably
a reason why magnetic microbeads have been used mainly for
concentration and isolation by retaining them within certain
regions of microchannels having a diameter smaller than that of the
microbead. Microfluidic pillars have also been used in microfluidic
channel systems as mechanical stoppers of microbeads. The
adsorption and desorption reactions between the partners of the
binding pairs as well as the purification stages, require
application of thorough and efficient mixing systems in order to
allow sufficient contact between the target binding partners in the
sample and their counterparts on the surface of microbeads or vice
versa. Therefore, in prior art, the adsorption/desorption steps and
purification steps are generally carried out before feeding the
liquid stream with processed target binding partners into the
microfluidic channel system for subsequent separation and
detection. In order to obtain adequate mixing in microfluidic
systems the application of physical forces, such as acoustic forces
have been suggested, but methods particularly aiming at
manipulation of magnetic microbeads in the microfluidic channels
are not suggested.
Gas bubble generation caused by electrical fields in aqueous
solutions is discussed in U.S. Publ. Appl. No. 2006/0228749, and
various physical forces are suggested for handling the problem, but
the fact that bubble formation is a frequently encountered
difficulty whenever a liquid stream is fed into a microfluidic
channel system is not discussed, even if air bubbles in a
microscale system, where the volume of a bubble is very big as
compared to the volume of the liquids fed into the system, is a
problem that can seriously distort any results obtained by using
microfluidic methods.
SUMMARY OF THE INVENTION
The object of the present invention is to improve the performance
and efficacy of assays by manipulating magnetic microbeads in
microfluidic chip devices. Improved efficacy and sensitivity is
achieved by the microfluidic microchip device of the present
invention, wherein the bubble formation in the liquid stream and
clustering of magnetic microbeads is prevented by allowing the
liquid stream first to pass a microfluidic pillar filter in a
reaction chamber of the microfluidic channel system and thereafter
the liquid stream meeting the magnetic microbeads in the channel
system are transported through another microfluidic pillar system,
thereby disintegrating or disassembling the clustering magnetic
microbeads. The applicability of the microfluidic chip device is
further increased by providing the device with holes for steering
rods on so called steering plate, which together with for example
liquid connections and electric needles facilitate exact fitting of
further electric and fluidic contacts between the microfluidic chip
device and external equipment on a measurement interface. The
microfluidic chip device and the measurement interface with the
steering plate are all placed on a stabilizing bottom, a so called
docking station. The steering rods on the steering plate and the
holes on the microchip devices facilitate exact fitting of electric
and/or fluidic connections between the external equipment and the
microfluidic chip device. This is particularly useful if the
microfluidic chip device is not provided with fully integrated
means for carrying out binding assays, isolation, concentration,
separation, detection, as well as PCR and decrease of background
noise caused by redundant detectable label as well as detection of
target binding partners or their counterparts forming a binding
pair present in the sample to be analyzed.
The present microchip device has liquid connections or junctions
and comprises or is connected to electric fields, for controlling
conditions, e.g. temperature, surveillance of liquid streams by
conductivity, for separating processed reaction products from the
binding assay by capillary electrophoresis, magnetic rods for
moving magnetic particles and optic instruments for recording the
reaction products. The microfluidic channel system comprises one or
more sealable tubular channels or passages having ports or liquid
connections, which may act both as inlets or outlets and can be
closed or opened by said liquid connections or junctions, which are
provided with seals. The microchannel system further comprises one
or more, preferably two, enlarged reaction chambers or cavities,
which are broader or deeper than the tubular channels of the
system. The reaction chambers are provided with one or more
microfluidic pillar filters for removing bubbles and for
disintegrating clusters of magnetic microbeads to which target
analytes and further reactants or reagents are attached or may be
attached during reactions taking place while the magnetic
microbeads are transferred from one part of the channel to another.
After a thorough mixing by the transfer the magnetic microbeads
with captured reagents, while one solution is removed and replaced
by another, the analytes or reactants captured on the magnetic
microbeads are trapped on the microfluidic pillar filter or behind
it. This trapping prevents the magnetic microbeads from escaping
with the drainage flow during the continuous or discontinuous
feeding of sample, reagent or washing solutions. The whole
microfluidic chip device may be provided in centimeter, millimeter
or nanometer scale.
The present invention is particularly related to a microfluidic
chip device for manipulating magnetic microbeads in a microfluidic
channel system. The microfluidic chip device is either an
integrated microfluidic chip device, which is provided with all
equipment needed for carrying out all the tasks required in a
typical binding assay or it is externally connected through a
measurement interface to the equipment needed for carrying out said
tasks. The equipment are magnetic, electric, and optic equipment
and the tasks include isolation, concentration, binding assays with
adsorption and desorption reactions, separation and detection and
further include, automatic or semiautomatic recording and software
applications for calculating the final results.
In addition to a tubular channel, the microfluidic channel system
preferably comprises two reaction chambers (101 and 102), but may
comprise only one reaction chamber in which case the microfluidic
channel may be used for some of the reaction steps, e.g.
PCR-reactions and concentration. The microfluidic channel system is
provided with one or more sealable fluidic connections (201, 202
and/or 203), which may be used both as inlets and outlets, while
the direction of the flow may be reversed. The liquid streams
include sample solutions, reagent solutions, washing solutions, or
eluents fed into the system. As shown in FIG. 2, which demonstrates
one preferred embodiment of the invention, connection (201) is the
inlet, connection (202) the outlet and connection (203) is used to
recover the processed liquid solution or to concentrate the
solution before leading it to means for separation and detection
(600 and 700). The target binding partners recovered after
processing may be amplified and/or concentrated before they enter
the capillaries used for separation and detection. The liquid
connections may be used in a reversed order depending upon the
configuration of the microfluidic chip device and the location of,
the integrated fluidic, electric and optic equipment provided on
the microfluidic chip device as well as the ultimate application of
the microfluidic chip device.
In the preferred embodiment of the invention shown in FIG. 2, the
microfluidic channel system comprises two reaction chambers (101
and 102), each of which are provided with at least one microfluidic
pillar filter (301 and 302). Microfluidic pillar filters are
diminutive scaffolds or arrays of quadrangular or round rods (303)
as shown in FIG. 3. These scaffolds are placed so that the
interspaces or spacings (304) between the rods are bigger than the
diameters of the magnetic microbeads. Typically, the interspaces of
the microfluidic pillars are in a scale of about 20 .mu.m to about
30 .mu.m, preferably about 25 .mu.m, but naturally the sizes may
vary according to the size of the microfluidic chip device.
The preferred magnetic equipment for manipulating magnetic
microbeads (401), which tend to form clusters (402) as shown in
FIG. 1, comprise an external magnetic rod (403), but may include
other electromagnetic forces. By moving the magnetic rod over the
microfluidic chip device and the microfluidic pillars therein, the
magnetic microbeads are transferred within the microfluidic channel
system and clustering is prevented.
The preferred electric equipment comprises electric needles and/or
electric thin film elements or thin film pads (501), which act as
heating elements (502), temperature measurement elements (503),
high voltage elements (504) or conductivity measurement elements
(505) The sealable fluidic connections (201, 202 and/or 203) are
preferable fluidic connectors with seals (204), but may be
injection needles.
The microfluidic channel system are provided with integrated or
externally connected separation equipment, such as straight or
looped capillary channels for chromatographic separation using
capillary electrophoresis with or without an isatachophoresis
pre-separation step.
For detection, the microfluidic chip device is provided with
integrated or externally connected equipment for detection
comprising optic or electric detectors including equipment for
measuring fluorescence, UV/VIS absorption, IR, conductivity or
refraction index as well as mass spectrometers.
The externally connected microfluidic chip device, which preferably
consists of two layers (801 and/or 802) and supports the
microfluidic channel system, which is placed between the two
layers, is easily connectable by using the perforated holes (804)
to the external equipment comprising a measurement interface (901)
with a steering plate (902) having steering rods (903). The
microfluidic chip device is provided with preferably perforated
holes (804), which allow easy and exact contacting between the
external equipment, electric needles (501), electric pads (501),
fluidic connections (201, 202 and/or 203) and the microfluidic chip
device.
In the two chamber microfluidic channel system, the microfluidic
pillar filter (301) in one of the reaction chambers (101) prevents
bubble formation in the liquid flow fed to the microfluidic channel
system and the other microfluidic pillar filter (302) in the other
reaction chamber (102) acts as a disintegrator of magnetic
microbeads (401) clusters (403). When a single chamber microfluidic
channel system is used, the at least one microfluidic pillar filter
provided therein may function to both prevent bubble formation and
disintegrate microbead clusters. Alternatively, the single chamber
microfluidic channel system may include more than one microfluidic
pillar filter, where one microfluidic pillar filter prevents bubble
formation, and another microfluidic pillar filter disintegrates
microbead clusters.
The microfluidic chip device has sealable fluidic couplings, which
preferably are fluidic connectors or injection needles constructed
for this purpose and which are provided with leakage preventing
seals (204).
The invention is above all related to a more effective method for
manipulating magnetic microbeads in a microfluidic channel system.
This method prevents cluster formation of magnetic microbeads and
thereby increases the free reactive surface on the surface of the
microbeads. In the method of the invention a liquid stream is fed
to a first reaction chamber (101), wherein a microfluidic pillar
filter (301) removes air bubbles and subsequently the liquid
streams is contacted with magnetic microbeads (401), which when a
magnetic rod (403) is switched on, may be forced through a
microfluidic pillar filter (302), which disintegrates the clusters
formed by the magnetic microbeads (401), which have diameter
smaller than the interspaces (304) between the rods (303) in the
microfluidic pillar filters (301 and 302).
The present invention is also related to methods for carrying out
binding assays using said method for manipulating magnetic
microbeads. The binding assays comprise at least one binding
reaction between a pair of binding partners or binding moieties on
magnetic microbeads and are useful for performing miniaturized
immunoassays or hybridization reactions for determining the
presence or absence of genomic sequences, mRNA, or ribosomal RNA.
The binding assays are not limited to detecting or measuring only
one binding pair but can be used for simultaneous determination of
plurality of binding pairs, so called multiplexing.
Methods for quantify and detecting one or more polynucleotide
sequences, which methods are applicable in microfluidic chip
devices are described in U.S. Publ. Appl. No. 2004/0053300, U.S.
Pat. No. 7,361,461, U.S. Publ. Appl. No. 2003/0129589, U.S. Publ.
Appl. No. 2003/0082530, U.S. Publ. Appl. No. 2006/0035228, U.S.
Pat. No. 5,514,543, U.S. Publ. Appl. No. 2005/0214825, U.S. Publ.
Appl. No. 2004/0121342, PCT Publ. Appl. No. WO 02/33126, PCT Publ.
Appl. No. WO 2004/063700, as well as in the publications Kataja et
al, J Microbiol Methods, October 2006, vol. 67, 102-113, and in
Pirrung et al., Bioorg Med Chem Lett, September 2001, vol. 11,
2437-2440. Further conventional binding assays which have been,
applied or can be used in microfluidic systems are described in the
patent literature (U.S. Publ. Appl. No. 2002/0076825, U.S. Publ.
Appl. No. 2002/0123134, U.S. Publ. Appl. No. 2004/0005582, U.S.
Publ. Appl. No. 2004/0969960, U.S. Publ. Appl. No.
2006/0228749).
The method also allows detection and determination of the amounts
of target sequences and genetic variations including single
nucleotide polymorphism (SNP) as described in U.S. Publ. Appl. No.
2009/0011944. The method is particularly adapted for performing
transcript analysis by aid of affinity capture (TRAC) assays as
described in U.S. Publ. Appl. No. 2004/0053300 and U.S. Pat. No.
7,361,461 and for determining antibodies and antigens as well as
fragments thereof.
Throughout this application, various patents and publications have
been cited. The disclosures of these patents and publications are
hereby incorporated by reference in their entireties into this
application, in order to more fully describe the state of the art
to which this invention pertains.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a schematic illustration of a cross-section of a
microfluidic chip device with fluidic and electric connections and
an externally placed magnetic rod for the manipulation of the
cluster of microbeads.
FIG. 2 is a schematic representation of a top view of a
microfluidic channel system with two reaction chambers.
FIG. 3 schematically depicts a three-dimensional perspective view
of a latitudinal and longitudinal cross-section of one of the
microfluidic reaction chambers demonstrating the construction of a
microfluidic pillar filter, which comprises miniature rods.
FIG. 4 is a schematic representation of a cross-section of a
microfluidic chip device placed on a steering plate with
measurement interface and further supported by a docking
station.
FIG. 5A illustrates a top view of a quadratic microfluidic chip
device with two reaction chambers.
FIG. 5B illustrates a bottom view of the quadratic microfluidic
chip device shown in FIG. 5A.
FIG. 5C is a top view of the silicon layer of a rectangular
microfluidic chip device with a typical array of electric contact
pads, equipment for PCR and a straight channel for capillary
electrophoresis.
FIG. 5D is a top view of the glass layer of a rectangular
microfluidic chip device with an array of electric contact pads
differing from that shown in FIG. 5C and equipment for PCR and a
straight channel for capillary electrophoresis.
FIG. 5E is a top view of a rectangular microfluidic chip device
with an array of electric contact pads differing from those shown
in FIGS. 5C and 5D and equipment for PCR and a straight channel for
capillary electrophoresis.
FIG. 5F is a bottom view of a microfluidic chip device
corresponding to those shown in FIGS. 5C to 5E with electric
contact pad arrays seen on the bottom and equipment for PCR and a
straight channel for capillary electrophoresis.
FIG. 5G is a schematic representation of a top view of a
rectangular microfluidic chip device with a CE-channel formed as a
loop and a microfluidic channel system.
FIG. 5H is a schematic representation of a top view of a quadratic
microfluidic chip device with looped CE-capillaries.
FIG. 6 is a schematic representation of a cross-section of a liquid
needle.
FIG. 7 is a schematic representation of a set up of microfluidic
chip device with auxiliary equipment.
DETAILED DESCRIPTION OF THE INVENTION
When using microfluidic on-chip systems for performing biological
solid phase assisted binding assays in connection with magnetic
microbeads, the magnetic microbeads have a tendency to cluster.
Clustering prevents the target binding partners present in the
sample from being efficiently attached to the surface of the
magnetic microbeads and also prevented effective purification in
the washing steps. In accordance with one aspect of the invention,
clusters of magnetic microbeads could be disintegrated or
disassembled by forcing the magnetic microbeads through a
microfluidic pillar filter. By manipulating said magnetic
microbeads their surfaces were liberated and could be contacted
from all directions by the surrounding liquid solution flowing
through the microfluidic channel system and thereby the reactions
between the target binding partners and their counterparts were
improved and formation of immobilized binding pairs is increased.
The sensitivity of the binding assays was improved. In accordance
with another aspect of the invention, improved purification of the
immobilized binding pairs on the magnetic microbeads and removal of
unbound reactants and solutions was also achieved. Accordingly, the
reaction rates could be accelerated and the efficiency of the
binding assays was improved leading to more reliable and sensitive
results. According to another aspect of the invention, air bubbles
were disintegrated when the liquid was transferred through the
microfluidic pillars. This solved the problem of distorted results
caused by bubble formation.
Another aspect of the invention solves the difficulties that may be
encountered in the incorporation of the microfluidic chip devices
and the exact fitting of the diminutive liquid junctions,
electrodes of the microchip into the microfluidic apparatus. The
problem may be solved by providing the microfluidic chip devices of
the present invention with perforated holes for steering rods on
the measurement interface, which secured the fitting of the
junctions, when the holes were adjusted by placing them on the
steering rods of the steering plates so as to be penetrated by the
injection needles and electric needles at holes provided for said
equipment.
A microfluidic chip device is a diminutive microfabricated
apparatus wherein micro- or nanoliter volumes of fluid streams
including samples, reagents, washing and eluting solutions are
manipulated in microchannels on a platform or microchip. Fluid flow
is achieved by mechanical force, for example by pressure from
micropumps, injectors or by capillary electrophoresis. Microscale
fluidic behavior differs from macroscale behavior, and makes the
microfluidic chip devices particularly adaptable for so called
micro total analyze systems (.mu.-TAS), including separation,
capturing, isolation, focusing, enrichment, concentration, physical
disruption, mixing, sequencing, amplification and/or binding assays
and reduction of background caused by redundant detector label.
An integrated microfluidic chip device comprises all elements
needed to perform sequential solid liquid phase binding and
releasing steps in micro-scale structures, which are fabricated in
or otherwise closely attached on the microfluidic chip device and
include channels, reaction chambers, electrode elements,
electromagnetic elements, scaffolds, separation equipment, and
optic elements The integrated microfluidic chip devices facilitate
physical, biophysical, biological, biochemical, or chemical
reactions including binding reactions, adsorption, washing,
desorption, multiplication, concentration, separation, detection,
etc. The microfluidic chip device is a platform, which supports the
fluidic micro-scale structures. It may have various shapes or
configurations and it may vary in length, breadth as well as in
height or depth. It can be quadratic, rectangular, circular,
elliptic, or have another useful irregular shape. The size of the
major surface of microfluidic chip device can vary considerably,
for example from about 0.5 cm.sup.2 to about 10 cm.sup.2 with a
characteristic dimension from about 1 cm.sup.2 to about 5 cm.sup.2.
The microfluidic chip devices may include channels or reaction
chambers fabricated between the surfaces of their layers.
An externally connected microfluidic chip device may be placed in
or on a steering plate connected to auxiliary external equipment
and connects the microfluidic chip device to external magnetic,
electric or optic equipment that control the functions of the
microfluidic chip device through the measurement interface
supported by a docking station (800). Together the measurement
interface and the microfluidic chip device enable total analysis in
microliter scale.
The microfluidic chip device may comprise one or more layers, and
preferably comprises two layers, a bottom layer and a top layer.
The bottom layer may be made of a non-transparent, moldable, solid
or semisolid porous or non-porous chip material, such as silicon,
rubber, glass, ceramics, plastics, polymers, or copolymers. The
upper layer is preferably transparent and may be made of glass,
quartz, Pyrex, or borosilicate, but silicon provided with windows
may be used as well. Polymer microfabrication, replication
techniques, direct fabrication with casting or molding can be used.
Optical lithographic patterning including the use of image masking
and hot embossing are examples of some applicable systems in
microfabrication.
According to one aspect of the invention, the upper and the lower
surfaces of the one or more layers of the microfluidic chip device
may be provided with depressions, including dents, grooves,
recesses and niches. The tubular channels for transporting the
liquid solutions can advantageously be fitted in the depressions on
the upper side of the lower layer. On the lower side of lower
layer, electric circuits and electrodes may be advantageously
soldered and located so as to fit to the junctions connecting the
microchip device. Different etching schemes are used for producing
the depressions for channel shapes. These shapes can also be made
by powder blasting, or laser ablation. These methods are, however,
not widely used, because etching of the silicon layer is so easy
and the preferred bottom layer is usually made of silicon.
Preferably the silicon layer is a wafer or a thin slice of
semiconducting material, such as a silicon crystal, upon which
microcircuits are constructed by doping, diffusion, ion
implantation, chemical etching or deposition of various metals.
Wafers are of key importance in the fabrication of semiconductors
such as integrate circuits, but are also convenient for fabricating
microfluidic chip devices.
The two layers of the microfluidic chip device are preferably
tightly closed or sealed. According to one aspect of the invention,
no leakage from between the layers is allowed. Polydimethylsiloxane
(PDMS) is a particularly useful material for closing any channel
systems. The layers are welded, pressed, or glued together.
Preferred methods are the use of adhesive bonding, thermal bonding,
or solvent bonding. The layers are perforated before or after the
layers are joined together. The perforated holes are located so as
to fit to the microfluidic chip steering plate in the measurement
interface with its electric, fluidic, and/or magnetic control
equipment as well as the optic detector contacts, everything
preferably supported by a docking station.
The microfluidic chip device is a platform, which supports the
microfluidic channel system with microchannels, and reaction
chambers. The microfluidic channel system is a miniaturized channel
system, which comprises elongated tubular channels and reaction
chambers in which processes, such as physical, chemical,
biological, biophysical or biochemical processes including
adsorption and desorption reactions are carried out. The
microfluidic channel systems enable fluid streams to be introduced
or injected or pumped from an external source and to be processed
in said microfluidic channel system, which comprises at least one,
but preferably more fluidic or liquid connections or ports acting
as inlets and/or outlets and leading to the reaction chambers.
A microfluidic channel system can comprise any material that
permits the passage of a fluid through it. Preferably, the channel
is a tube made of rubber, Teflon (polytetrafluoroethylene), or
another useful material. Preferably, it should be made of a
biocompatible material or a material that can be made
biocompatible. A microfluidic channel system can be of any
dimensions, which depends on the size of the chip device, but
generally it is in microscale, ranging from 10 microns up to 1
millimeter in internal diameter.
A channel is a structure in a chip with a lower surface and at
least two walls that extend upward from the lower surface of the
channel, and in which the length of two opposite walls is greater
than the distance between the two opposite walls. A channel
therefore allows for flow of a fluid along its internal length. A
channel is preferably a covered tunnel.
A reaction chamber is a depression or small cavity or well on the
surface of the microfluidic chip device that is capable of
containing a liquid or fluid sample. The reaction chamber has a
lower surface surrounded on at least two sides by one or more walls
that extend from the lower surface of the channel. The walls can be
of any form, but generally they extend upward in a sigmoidal,
curved or multi-angled fashion. The lower surface of the reaction
chamber and the tubular can be at the same level as the upper
surface of a chip or higher than the upper surface of a chip, or
lower than the upper surface of a chip. The sides or walls of the
reaction chamber or channel may be made of other materials than
those that make up the lower layer of the chip. In this way the
lower surface of the chip can comprise a thin material through
which electrical, electromagnetic forces can be transmitted, and
the walls of one or more reaction chambers or channels may comprise
insulating materials that prevent the transmission of electrical
forces. The walls of the reaction chambers and the channel may be
made of any material, including silicon, glass, rubber, and/or one
or more polymers, plastics, ceramics, or metals. Preferably, the
channels and reaction chambers are made of a biocompatible material
or a material that can be made biocompatible and wherein the target
binding partners and other reactants are manipulated on magnetic
microbeads.
A fluidic or liquid connection, which may act both as an outlet or
inlet is an opening or port to the microfluidic channel system
comprising a tubular channel and one or two reaction chambers
through which a fluid sample can enter or exit the chamber. The
seal is preferably controlled by electric or magnetic forces or a
combination thereof. The port can be of any dimensions, but
preferably it is of a shape and size that allows a sample to be
transported through the port by physical forces, or dispensed
through the port by means of a pipette, syringe, injection needle
or other means of applying a sample. Sealable fluidic connections
are ports acting as inlets and/or outlets for liquid streams. They
can be closed mechanically, or by injection needles, or fluidic
connectors specifically constructed for microfluidic systems (U.S.
Pat. No. 6,319,476). A typical injector useful in the present
invention is shown in FIG. 6.
Microfluidic pillar filters are miniaturized scaffolds comprising a
plurality of very small rods fabricated in the microfluidic channel
system. Previously, such miniature rods have been used in
microfluidic systems as mechanical barriers for retention of
microbeads. In the present invention the microfluidic pillar
filters are not solely used for retention of microbeads, they are
particularly applied for disintegration of clusters of magnetic
microbeads and for preventing air bubble formation in the solutions
fed into the channel system. The rods, which may be quadruples or
may have round, elliptic or oval cross-sections may be made in
macro-, micro- or nano-size and may have a height of approximately
from one to five millimeter and the diameter of its cross-section,
which can be circular or quadratic, is from approximately 20
micrometer to approximately one millimeter. Naturally, the size
depends upon the size of the microfluidic chip device and can be in
micrometer dimension as well. In accordance with one aspect of the
invention, the microfluidic pillar filters of the present invention
preferably have interspaces, which are bigger than the diameters of
the magnetic microbeads and allow them to pass through the
barrier.
The magnetic microbeads may be manipulated with magnetic forces
exerted by any suitable magnetic apparatus. Magnetic forces are
forces exerted on magnetic microbeads by a magnetic field, which
may be provided, for example, by a magnetic rod. In accordance with
one aspect of the present invention, the preferred magnetic
equipment for manipulating magnetic microbeads may be an external
magnetic rod. In the present invention manipulation of the magnetic
microbeads replaces mixing with any mechanical or acoustic means
for mixing. Sufficient movement of the separated magnetic
microbeads and the solution in the channel system is achieved in
order to allow sample, reagent or any other solution to contact the
surface of microbead and any substance immobilized on its surface
from all directions. By using the magnetic rod, which forces the
magnetic microbeads through the pillar filters in the reaction
chambers, the components, in the samples, reagents and other
solutions and the surface of the magnetic microbeads become
sufficiently interspersed.
Magnetic forces refer to the forces acting on a magnetic microbead
due to the application of a magnetic field. Particles have to be
magnetic or paramagnetic to provide sufficient magnetic forces for
manipulation of the particles. A typical magnetic particle is made
of super-paramagnetic material. When the particle is subjected to a
magnetic field a magnetic dipole is induced in the magnetic
microbead or particle. To achieve a sufficiently large magnetic
manipulation force, the volume susceptibility of the magnetic
microbeads should be maximized, the magnetic field strength should
be maximized, and the magnetic field strength gradient should be
maximized.
In the present invention paramagnetic microbeads are preferred,
because their magnetic dipoles can be induced by externally applied
magnetic fields and returned to zero, when the external field is
turned off. Commercially available paramagnetic or other magnetic
microbeads may be used. These commercially available magnetic
microbeads have sizes from 0.5.mu. to 10.mu. or more. They may have
different structures and compositions. Magnetic microbeads may have
ferromagnetic materials encapsulated in thin latex or polystyrene
shells. Another type of magnetic particles has ferromagnetic
nanoparticles diffused in the latex or polystyrene surroundings.
The surfaces of both these particle types are polystyrene in nature
and may be modified to link to various types of molecules. They can
for example be affinity labeled or covered with avidin or
streptavidin, or some other affinity label.
The manipulation of magnetic microbeads requires the magnetic field
distribution to be generated over microscopic scales. One approach,
for generating such magnetic fields, is the use of
microelectromagnetic units. Such units can induce or produce a
magnetic field, when an electrical current, is applied. The
switching on/off status and the magnitudes of the electrical
current applied to these units will determine the magnetic field
distribution. The structure and dimension of the
microelectromagnetic units may be designed according to the
requirement of the magnetic field distribution. Manipulation of
magnetic microbeads includes the directed movement, focusing and
trapping of magnetic microbeads. Theories and practice regarding
the motion of magnetic microbeads in a magnetic field as well as
applications thereof may be found in the literature, including text
books.
As is evident from the description provided herein, the aim of the
present invention is to provide a novel and inventive method for
manipulating magnetic microbeads, but it does not exclude the use
of electric equipment in the microfluidic chip device
In accordance with one aspect of the invention, electric equipment
may include electric connections, particularly electric needles or
electric thin film elements or electric pads. The electric thin
film elements may act as heating elements, temperature measurement
elements, high voltage elements or conductivity measurement
elements. The thin film pads are generally round but may have any
other shape. Electrodes can also comprise doped semiconductors,
where a semiconducting material is mixed with small amounts of
other conductive materials.
In the present invention electrical forces may be used for
separation, for example in capillary electrophoresis. Electric
forces may also be used for the heating and temperature
measurements used when performing PCR-reactions, but temperature
adjustment and control are also important in all kinds of
bioassays. This is achieved by attaching electric connection on
both sides of the reaction chamber or the tubular channel electric
contact pads, by which the sample can be heated and the temperature
measured. Particularly, if the electric connections are attached on
both sides of the channel, a constant electric field is achieved by
aid of which both sample and magnetic microbeads may be moved. A
pair of electric pads or electrodes may also be used for
concentration of target partners before capillary
electrophoresis.
Dielectrophoresis may be used for performing binding assays with
antigen and antibodies and chemicals having affinity for each
other. A dielectrophoretic force is the force that acts on a
polarizable particle in a non-uniform electrical field.
Conventional dielectrophoresis is the movement of polarized
microbeads in non-uniform electrical fields. There are generally
two types of dielectrophoresis, positive dielectrophoresis and
negative dielectrophoresis. In positive dielectrophoresis,
particles are moved by dielectrophoresis toward the strong field
regions. In negative dielectrophoresis, particles are moved by
dielectrophoresis toward weak field regions. Whether microbeads
with immobilized target partners exhibit positive or negative
dielectrophoresis depends on whether the magnetic microbeads are
more or less polarizable than the surrounding medium.
The separation equipment in the microfluidic channel system is
provided with integrated or externally connected chromatographic
equipment comprising straight or looped channels performing
electrophoresis with or without isotachophoresis as a
pre-separation step. Capillary electrophoresis is particularly
convenient in the present invention. Isotachophoresis is a
technique used in analytical chemistry to separate charged
particles. It is a further development of electrophoresis. It is a
powerful separation technique using a discontinuous electrical
field to create sharp boundaries between the sample constituents.
In isotachophoresis the sample is introduced between a fast leading
electrolyte and a slow terminating electrolyte. After application
of an electric potential a low electrical field is created in the
leading electrolyte and a high electrical field in the terminating
electrolyte. The pH at sample level is determined by the
counter-ion of the leading electrolyte that migrates in the
opposite direction. In the first stage the sample constituents
migrate at different speeds and start to separate from each other.
The faster constituents will create a lower electrical field in the
leading part of the sample zone and vice versa. Finally the
constituents will completely separate from each other and
concentrate at an equilibrium concentration, surrounded by sharp
electrical field differences. Specific spacer or marker molecules
are added to the sample to separate physically the sample
constituents of interest. Isotachophoresis shows its superiority to
conventional separation techniques when the maximum resolution is
achieved with the latter. The choice of the experimental parameters
remains complex, but selection of appropriate parameters may be
made by consulting reference materials known to those skilled in
the art.
In the present invention, optic equipment includes means for
surveillance of the movement of target partners and for measuring
or detecting the target partners after a completed binding assay
has been performed. For detection, the microfluidic channel system
may be provided with integrated or externally connected equipment
comprising detectors including fluorescence detectors, laser
induced fluorescence detectors, mass spectrometers or equipment for
measuring UV/VIS absorption, IR, conductivity or refraction
index.
The microfluidic chip device of the present invention is preferably
an automatic system, which means that the system requires
substantially no manual procedures, such as pipetting or manual
transfer of samples or reagents, inversion or vortexing of tubes,
placing samples in a centrifuge or an incubator by a practitioner.
An automated system may, however, require manual application of the
sample to the system by pipetting or injecting, or manual recovery
of sample components that have been fully processed by the system
by collecting from tubes, wherein the reacted flow is collected. An
automated system may or may not require a practitioner to control
power-driven systems for fluid flow, to control power-driven
systems for generating physical forces for the performance of
processing and analysis tasks, to control power-driven systems for
generating physical forces for the translocation of sample
components, and the like, during the operation of the integrated
chip system, but these control measures may be computerized. An
automated system, such as an automated integrated biochip system of
the present invention, is preferably computer-driven.
In the present invention the magnetic field, particularly the
magnetic rod, exerts the forces only on magnetic particles and
target partners or binding pairs immobilized on magnetic particles.
The invention is not applicable to the use of non-magnetic
particles, e.g., polystyrene particles or beads. Accordingly the
present invention relates to microfluidic chip devices that utilize
magnetic microbeads.
According to one aspect of the invention the microfluidic pillar
filters are preferably controlled by one or more magnetic rods,
which enable the transfer of the magnetic microbeads from one
reaction chamber to another, thereby allowing the microbeads to be
contacted with fresh sample, reagent and washing solutions. The
magnetic microbeads to which analytes and reagents are
alternatively attached and released during the feeding of sample,
reagent and washing solutions are simultaneously prevented from
escaping with the stream of solutions, when the obsolete sample,
reagent, washing and other solutions are removed.
The microfluidic chip device, its structure, and its fabrication
are described in more detail by referring to the Figures.
FIG. 1 schematically illustrates a cross section of the
microfluidic chip device of the present invention. The microfluidic
channel system (100) comprises one or two reactions chambers (not
distinguishable in FIG. 1) in which magnetic microbeads (401)
forming clusters (402) are manipulated. The microfluidic channel
system (100) is provided with one or more microfluidic connections
or microfluidic needles (200), which preferably are sealable with
leakage preventing seals (204). The microfluidic channel system
(100) is provided with one or two microfluidic pillar filters. One
of the said microfluidic pillar filters (300) with pillars (303)
and their interspaces (304) are schematically shown in FIG. 1.
Magnetic microbeads (401) forming clusters (402) and a magnetic rod
(403) for manipulating the magnetic microbeads (401) are indicated.
The microfluidic chip device also comprises electric equipment
(500), including two electric needles (501) as well as other
electric thin film elements or pads (501). These elements comprise
heating elements (502), temperature measurement element (503), high
voltage elements (504), and conductivity measurement elements
(505). In a preferred embodiment of the invention the microfluidic
chip device (800) consists of two layers (801, 802). The bottom
layer (801) is preferably a silicon layer in which the microfluidic
channel system (100) is embedded and the upper layer is a
transparent layer, e.g. a glass-lid (802), which allows monitoring
of the stream of components from the binding assays carried out in
the microfluidic channel system (100). The lower layer of the chip
device is provided with holes (not shown in FIG. 1) for the
steering needles (903), electric needles (501) and liquid
connections (200) protruding from a steering plate (not shown in
FIG. 1). The upper layer (802) of the chip device preferably
comprises a straight or looped channel for performing separation
(600) (not shown in FIG. 1) and means for detection (700) (not
shown in FIG. 1).
FIG. 2 schematically illustrates a preferred embodiment of the
microfluidic channel system seen from above. The microfluidic
channel system comprises one or more, preferably two reaction
chambers (101 and/or 102) with three sealable liquid connections
(201, 202 and/or 203), which are sealable and act as inlets and/or
outlets for the liquid flow. In other words, liquid feeding may be
carried out from any of the liquid connections (201, 202, and/or
203) and it is also possible to reverse the chosen order and
direction of the flow. The reaction chambers (101 and/or 102) are
each provided with at least one fluidic pillar filter (301, 302).
The pillars of the microfluidic pillar filter consist of pillars or
rods, e.g. pillar rods (303) with spacings or interspaces (304)
having a size allowing the magnetic microbeads to pass at least one
by one. Liquid may be fed through connection (201), which may act
as the main feeding channel leading to reaction chamber (101) or
the so called bubble chamber, wherein air bubbles are filtered with
the microfluidic pillar filter (301). Thereafter, the liquid stream
contacts the clusters of magnetic microbeads, which may be
manipulated using an externally located magnetic rod (not shown in
FIG. 2). It is possible to move the magnetic microbeads back and
forth through the microfluidic pillar filter (302) in reaction
chamber (102) or through the microfluidic pillar filters (301) in
reaction chamber (101) or back and forth through both of the two
microfluidic pillars (301) and (302), thereby using both reaction
chambers. The presence of three liquid connections enable trapping
of the magnetic microbeads in any one of the reaction chambers (101
or 102) behind one of the pillar filters (301 and/or 302) or for
example in the channel (103) behind the pillar filter (302) or
pillar filter (301), when the liquid is replaced or changed in the
system or removed from the system, e.g. through the liquid
connection (202). After the introduction or injection of a new,
replacing liquid, comprising reagents, buffer or eluting solutions,
it is possible to transfer or move the magnetic microbeads back
into the newly introduced liquid solution (reagent, washing or
eluting solution) present in one of the reaction chambers by
switching on the magnetic rod. The magnetic microbeads tend to form
clusters and the magnetic particle clusters may be broken with
external magnetic rod (not shown in FIG. 2) by moving the external
magnetic rod over the pillar filters (301 and/or 302) of the
reaction chamber (101 and/or 102). The microfluidic pillar filters
(302) in the reaction chamber (102) are used for preventing
clustering of magnetic microbeads during reactions and purification
or washing. The electric equipment (500) of the microfluidic chip
device comprises electric thin film elements (501), which include a
heating element (502) and a temperature measurement element (503)
are placed across the reaction chamber (102) and high voltage
contacts (504), which are placed on both sides of the reaction
chamber (102) or on both sides of the microfluidic channel (103).
These electric equipment or electric thin film elements (500) may
be used for performing e.g. PCR-reactions after the completion of a
binding assay between complementary poly- or oligonucleotide
sequences and for concentration of the processed reactants
comprising either the desired components or target partners or
their counterparts, whichever it is desirable to determine of the
binding pair, after the desired binding reactions and before the
liquid with the processed reactants is allowed to enter the
capillary system for separation of the target partners or their
counterparts by capillary electrophoresis (CE) (600) followed by
recording and detecting (700) said target partners or reactants
with appropriate equipment. A further reaction chamber may be
placed immediately before the location, wherein the fluidic stream
enters the system for fractionation and detection. This further
reaction chamber may be used for PCR-cycles, and for providing the
target poly- or oligonucleotide sequences or the complementary
probe sequences with detectable labels and for diminishing or
reducing the background caused by redundant detectable labels by
performing two subsequent PCR-cycles, wherein each sequences to be
amplified is provided with two universal primers. The reduction is
achieved by initiating a first PCR-cycle e with a sequence provided
with a detectable label complementary to one of the universal
primers and initiating a second PCR-cycle with another sequence
which is provided with a sequence complementary to the other
universal primer. The now double-stranded probe sequence provided
with both detectable and affinity label are thereafter captured or
immobilized on magnetic microbeads. The double-stranded probe or
hybrid formed, which hybrids are provided with an affinity tag and
detectable label by contacting the hybrids with magnetic
microbeads, which are forced through the microfluidic pillar
filter. The magnetic microbeads are kept behind one of the
microfluidic pillar filters, while redundant liquids, reagents, etc
are removed through one of the outlets. The steps are thereafter
repeated with washing solutions. After this purification the probe
or target provided with a detectable label is eluted from the
hybrid on the magnetic microbead in a small volume of elution
solution. This concentrated solution comprising purified targets or
probes to be determined are led into the separation system and for
recording.
FIG. 3 depicts a three-dimensional perspective view of a
latitudinal and longitudinal cross-section of one of the
microfluidic reaction chambers (102) demonstrating the construction
of a microfluidic pillar filter (302). The microfluidic channel
system with reaction chambers is embedded in the bottom layer (801)
of the microfluidic chip device. In a preferred embodiment of the
invention the pillar rods (303) have, for example, when in
microscale, a height of about 350 .mu.m. They are rectangular, oval
or round in shape. One side is about 50 to 100 .mu.m if the pillar
rod is rectangular and the diameter is about 50 to 100 .mu.m if the
pillar rod is round. The rods are preferably placed with about 25
.mu.m spacings or interspaces, which allow magnetic microbeads
having a diameter of e.g. up to 10 to 20 .mu.m to pass through the
microfluidic pillar filter. All the dimensions provided herein are
only approximate dimensions. Accordingly, the dimensions may vary
depending of the size of microfluidic chip device and its
dimensions, which may vary between several centimeters down to
millimeters. Accordingly, they can be in micro- or macro-size.
FIG. 4 is a schematic illustration of the microfluidic chip device
(800), which is placed on auxiliary equipment (900) and may be
connected to such auxiliary equipment as software-associated
automatic or semiautomatic instruments in which the results
obtained are collected, and deposited for further calculations and
processing. The microfluidic chip device (800) is placed on a
steering plate (902) with protruding steering rods (903) connected
to a measurement interface (901) and the whole system is supported
by a docking station (904). The microfluidic chip device comprises
the microfluidic channel system embedded between two layers (801)
and (802). The microfluidic channel system (100) includes fluidic
connections or couplings (200), magnetic microbeads (401), electric
connections or couplings (500), including electric needles and
electric pads. The upper layer is transparent and may comprise a
fluorescence measurement window (701), means for performing a PCR
reaction or concentration (702) of the components in the solution
and equipment for performing a capillary electrophoresis (703). In
FIG. 4 the liquid connections (200), the steering needles (903) as
well as the electric equipment (500) comprising electrical needles
(501) or electric thin film elements for heating, for temperature
measurement, for providing high voltage concentration, and for
conductivity measurement are schematically illustrated as upright
rectangular boxes. The microfluidic chip device is placed on a chip
steering plate (902) by fitting the chip steering needles or
steering rods (903) into the holes on the chip device (not seen in
FIG. 4). The magnetic rod is not shown in FIG. 4. An optional air
cooling nozzle (905) is shown in FIG. 4. The bottom layer of the
microfluidic chip device is preferably a silicon layer (801)
supporting the microfluidic channel system (100) in depressions
therein and the upper layer (802) is preferably a transparent
layer, for example a glass cover with the electric equipment (500)
for heating, temperature measurement, provision of high voltage
concentration and conductivity measurement. The upper transparent
layer also comprises means for performing capillary electrophoresis
and means for detection.
FIGS. 5A-5H illustrate different types of microfluidic chip device
with different shapes, straight or looped channels and with
auxiliary electric and optic equipment placed in various positions
on the chip devices.
FIG. 5A illustrates a top view of a microfluidic chip device with
two reaction chamber (101 and 102), fluidic connections (201 and
202) and microfluidic pillar filters (301 and 302). Electrical
connections consisting of contact pads or thin film elements (501)
and electric wires (506) are shown in FIG. 5A. The microfluidic
chip device is provided with holes for the fluidic connections or
liquid needles (201 and 202), and with holes (803) for steering
needles.
FIG. 5B illustrates a bottom view of a microfluidic chip device the
upper view of which is shown in FIG. 5A. The bottom view of the
microfluidic chip device shown in FIG. 5B demonstrates contact pads
(501) and wires (506) for a heating element located on the lower
surface of the silicon layer. The holes for fluidic connections are
marked (201, 202). Holes (505) are for the electrical needles.
FIG. 5C depicts the structure of a microfluidic channel system
(100) in a microfluidic chip device for performing a polymerase
chain reaction-isotachophoresis-capillary electrophoresis
(PCR-ITP-CE) with a straight CE channel (600). FIG. 5C illustrates
a view of the upper side of the silicon layer. The structure of the
reaction chambers (101) acting as bubble filter and the reaction
chamber (102) acting as a disintegrator of microbead clusters as
well as the electric pads (501) for heating and temperature
measurement element are identical in all types of chips. The
positions of electric contact pads for the heating and temperature
measurement elements may vary. The PCR-ITP-CE chips have thin film
elements (501) also for high voltage and conductivity detection.
The conductivity detection electrodes have two parallel 20 .mu.m
electrodes with 20 .mu.m spacing. The length of the straight CE
channel (600) is about 33 mm. The fluidic connections are marked
(201, 202 and/or 203) and the pillar filter (301 and/or 302). The
holes for the steering wheels are marked (803).
FIG. 5D is a view of the upper side of the glass layer. The glass
layer has holes (803) or cavities for the steering needles and
electric contact pads (501) or holes for the electric needles (501)
and electric wires (506) and the microfluidic channel system (100)
with fluidic connections (201, 202, 203), wires (506) and gel
electrophoresis, PCR and ITP-channels (600) as indicated in FIG.
5C.
FIG. 5E is a view from the upper side of the chip showing equipment
in the glass layer and in the silicon layer seen through the glass
layer with minor variations.
FIG. 5F is a bottom view of the microfluidic chip device shown in
FIG. 5E. The PCR-ITP-CE chip has 7 holes for fluidic connections or
couplings, 14 holes for electrical couplings (805) and 3 holes for
steering needles (803). The location of connections and pads may
vary.
FIGS. 5G-5H demonstrate sample injection systems for CE/ITP
microfluidic chip devices.
FIG. 5G illustrates a view of the upper side of the silicon layer
with a straight CE-channel and a microfluidic channel system,
wherein sample injection is carried out with pressure injection,
but it is also possible to use electrical injection simultaneously
with pressure injection. The pressure injection from the reaction
chamber (202) into the sample loop (600) may take place
simultaneously with the electrical injection to the sample loop
(600). Electric contact pads or electrodes for conductivity
detection (505) are shown as well as thin film electric wiring
(506). The conductivity measurement electrodes may be used for
monitoring the sample injection or the concentration in the CE
channel. It is possible by simultaneously applied pressure and/or
electrical injection to stop a sample concentrate between two
parallel electrode pairs. The sample injection loops of devices in
the Figures are 4.1 mm (23 nl) and: 6.3 mm (35 nl), respectively,
but may vary depending on the size of the microfluidic chip device
The distance from ITP output to the end of CE channel is 22.5 mm.
The sample injection loop is placed in double T junction at a
position 100 .mu.m from center to center. The distance from the
double T to ITP output may preferably be 9.8 mm and the distance
from ITP output to the end of CE channel may be 22.5 mm. A sample
injection loop with a serpentine shape CE channel, wherein the
sample injection loops may be 4.1 mm and 9.6 mm. The distance from
ITP output to the end of CE channel may be for example 58 mm.
FIG. 5H illustrates a view of the upper side of the silicon layer
with a CE-channel formed as a loop and a microfluidic channel
system, wherein sample injection is carried out with pressure
injection, is a view of the upper side of the glass layer. The
glass layer has holes (803) or cavities for the steering
needles.
FIG. 6 is a schematic illustration of a liquid needle (200), which
is located in the same for example 3 mm.times.3 mm matrix as the
electrical needles (not shown). The cross-section of the
microfluidic chip device is shown in the upper part of the FIG. 6
as the silicon layer (801) and the glass layer (802). The
structures of liquid needles and the steering needles are
preferably made of steel pipes. A plastic pipe cover steers the
liquid needle (200) to the coupling hole on the microfluidic chip
device. The plastic pipe steering is based on taper bolt in a
steering plate. The liquid needle has a rubber seal in the head of
the liquid needle.
FIG. 7 demonstrates the set up of a microfluidic chip measurement
set up or a measurement system comprising temperature controlling
and fluorescence/conductivity detection. Temperature and
fluorescence data is synchronized. Temperature measurement setup is
controlled with an AD/DA driver card of PC. The driver card
measures the thermistor temperature and controls the heating power
of heating element. The fluorescence measurement setup is
controlled commercial program (Hamamatsu Wasabi) and LabView
software chip measurement setup.
As described above, the microfluidic chip device is a platform,
which may include a bottom layer and a top layer, which support the
microfluidic channel system between the layers. The upper layer is
preferably a transparent glass layer, but quartz or borosilicate
may be used. The upper layer may consist of about 200-1000 .mu.m,
preferably 400-700 .mu.m, most preferably about 500 .mu.m thick
wafers. The surface below the upper layer may be provided with
grooves. The tubular channels for transporting the liquid solutions
can advantageously be fitted on the grooves located on the side
which is below the lower layer. Tubular channels may have
associated capillary grooves in the lower layer, but capillary
grooves could also be located in the lower surface on the upper
layer. The tubular channels, which may be made of glass or inert
plastics or other materials such as metal (for example steel), have
a diameter of approximately 10-1000 .mu.m, preferably 200-450
.mu.m, most preferably about 350 .mu.m, and are preferably
biocompatible or can be made biocompatible.
The lower layer is preferably made of silicon or polymers, but
other materials can be used. The lower layer has a thickness of
about 200-1000 .mu.m, preferably 400-700 .mu.m, most preferably
about 500 .mu.m. The upper and the lower surfaces of the
microfluidic chip device may be provided with shaped depressions or
grooves, which support the microfluidic channel system. The tubular
channels may further include reaction chambers for transporting the
liquid solutions, which can advantageously be fitted in the
depressions or grooves on the upper side of the lower layer. On the
lower side of lower layer electric circuits and electrodes are
advantageously soldered and located so as to fit to the junctions
connecting the microchip device and the apparatus providing
external streams of solutions, electric and magnetic power and
leading to separation devices and optic detection instruments.
The top or upper layer and the bottom or lower layer, are joined
together in chip level or they are fusion bonded in so called wafer
level. Anodic bonding in wafer level and laser bonding in chip
level are alternative methods for joining the layers. Glue bonding
may be done by screen printing, whereby glue is printed through a
screen to the surface of the bottom layer, which preferably is made
of silicon. After screen printing, the upper layer, which
preferably is a glass layer, may be joined to the silicon bottom
layer. The glue or adhesive material may be cured in a furnace or
another suitable curing apparatus. In fusion bonding argon gas is
used for activation of wafers. After surface activation the top and
bottom layers, which may be, for example, silicon and glass wafers,
respectively, are joined together. Fusion bonding is strengthened
by heating in a furnace having a temperature of about
100-400.degree. C.
In a preferred embodiment of the invention, the microchip may be
manufactured substantially as described below, although any other
suitable manufacturing method may be used in connection with the
present invention. The fabrication of the microchip device of the
present invention starts from blank silicon and silica wafers, the
diameter of which is preferably about 100 mm, and the thickness of
which is preferably approximately 525 .mu.m. The front sides of the
silicon wafers are subjected to thermal oxidation,
photolithography, oxide etching, Plasma Enhanced Chemical Vapor
Deposition (PECVD) silicon nitride deposition, photolithography,
PECVD oxide deposition, photolithography, oxide etching and final
photolithography. During these processing steps, a three-level
plasma etching is conducted to a depth of 75 .mu.m, and 375 .mu.m,
respectively and also through the 525 .mu.m silicon wafer. Finally
the silicon wafer with the feed-through holes is thermally oxidized
to form an electrical insulation.
The silicon layer (801) supports the microfluidic structures
including channel and reaction chambers (100) in which the magnetic
microbeads (401) are manipulated and the binding assays are carried
out. Polymerase chain reaction (PCR), concentration and/or
capillary electrophoresis (CE) may be performed in connection with
the binding assays to further improve the performance. For PCR and
CE the microfluidic chip device is provided by thin film elements
(501) for heating. These may be made of molybdenum and provided
with a cover layer of Plasma Enhanced Chemical Vapor Deposition
(PECVD) and aluminum contact pads. The silicon layer is also
provided with thermal oxide electrical insulation, holes for
electric contact needles (501), fluidic needles (201 and/or 202,
etc) and steering needles or rods (903). The upper glass layer
(802) comprises an electric element (501) for temperature
measurement, for providing high voltage and conductivity detection.
The thin film elements (501) on the upper glass layer (802) are
preferably made of platinum and are provided with a cover layer of
PECVD oxide. The PECVD oxide can be opened in a contact point or in
a measurement point (window).
The back side of the lower layer or the silicon wafer is first
coated with molybdenum, which is then patterned by plasma etching
after photolithography, to form heaters with contact pads. A cover
of oxide is formed using (PECVD), and subsequently the oxide cover
is partially etched on to uncover the contact pads.
The bottom layer or silica layer, which preferably is a silicon
wafer provided with a patterned photoresistance, which enables a
subsequent lift-off procedure of platinum. After the lift-off, the
thermistors and conductivity detection circuitry are formed.
Thereafter, a cover oxide is formed using PECVD, which is then
etched partially to uncover the contact pads for needle contacts
through the silicon wafer and to uncover the conductivity detection
tips. As a final step, alignment dents are etched to each silica
cover of the microchips for steering needles. Then the silica and
silicon wafers are sawed into microchips and subsequently bonded
with an adhesive.
Utility
The present invention provides accurate assessment of the effects
and biological role of binding substances, such as nucleic acids,
proteins, antibodies, antigens or enzymes. The rapid and accurate
methods for determining diminutive amounts of a plurality target
analytes and providing quantitative computer readable results
including transcriptional profiles are useful in medicine and
pharmaceutical industry. The effects of known and novel drugs on
the gene expression of human beings and experimental animals can
easily be measure and provide essential knowledge for
pharmaceutical and diagnostic industry as well as in health care
including hospitals and health centers. The main utility being to
provide useful information for health care, treatment modalities,
pharmaceutical applications in a form that may be computerized and
handled in a numerically exact manner.
The present invention provides a more versatile system for
performing miniaturized, rapid and effective hybridization,
polymerase chain reaction or amplification assays and immunoassays,
which assays all apply a combination of liquid phase and solid
phase stages. The rapid and effective purification is achieved in
an on-chip device with the microfluidic channel system. The tubular
channels of the microfluidic channel systems are provided with
enlarged reaction chambers or cavities having microfluidic filters
or grids controlled by magnetic rods. The microfluidic filters are
capable of disintegrating or disassemble the clusters of magnetic
microbeads by forcing the particles through the filter. At the same
time the inventors noted that air bubbles, which severely distort
results measured in a diminutive step could be avoided by using
said pillar filters.
The present invention is related to an analytic microchip device
having a multi-channel system for performing rapid and effective
solid liquid phase binding assays of one or more binding substances
from sample solutions, including cell lysates and mixtures of
products obtained for example by combinatorial chemistry.
The microfluidic chip device is useful for increasing the reactive
free surface on magnetic microbeads when manipulating the magnetic
microbeads in binding assays. Manipulation refers to moving or
processing of the target partners and their counterparts on
magnetic microbeads. Target binding partners that are manipulated
by the methods of the present invention are coupled to their
counterparts and together they form binding pairs. The
manipulations include transportation or movement, capturing,
focusing, enrichment, concentration, aggregation, disintegration,
trapping, separation, or isolation. For effective manipulation of
target binding partners forming binding pair complexes, the binding
pairs and the magnetic force used must be compatible.
The sequential manipulation steps may comprise mixing,
concentration, dilution, washing and binding and releasing steps,
which facilitate the binding assay in a microfluidic chip device.
The steps include reactions, washing, releasing (denaturation,
elution), separation, and analysis tasks. The efficiency of said
steps depends on effective disintegration of clustering magnetic
microbead. The disintegration facilitates dispersion and/or binding
of sample components including target binding partners and their
counterparts forming binding pair complexes and simultaneous
transportation of said components from one part of one reaction
chamber to another part of the reaction chamber separated by a
microfluidic pillar filter.
The microfluidic channel system is particularly useful for
performing assays with analytes which may be binding partners
having counterparts, for example antibodies and antigens, which
have a specific affinity to each others. Together the binding
partner and its counterpart form a binding pair, for example
antibodies and antigens or fragments thereof, single-stranded
target poly- or oligonucleotide sequences and single-stranded
probes, which are complementary to the target poly- or
oligonucleotide sequences, may form such complexes. A binding
partner and its counterpart, i.e. two binding partners which may
form a binding pair, are each separately or alone or as a complex
provided with an affinity tag and thereby they may be collected or
immobilized on a magnetic microbead covered with another affinity
label having affinity to the corresponding affinity tag. Thus the
magnetic particles, which have immobilized one binding partner may
collect the counterpart which may or may not carry a detectable
label of said binding partner and thereby form an immobilized
binding pair complex.
Usually the target binding partner is the component which is to be
determined from a sample. It is the desired component or the
component of interest in the assay. It can be processed, e.g.
isolated before entering the microfluidic chip device, but it can
be directly introduced, if it is soluble or solubilizable in the
sample media, buffer solution or eluting solution used in the
binding assay.
The target binding partner can be any organic or inorganic
molecule, which has a specific affinity for another molecule, which
is its counterpart. Useful target binding partners can be amino
acids, peptides, proteins, glycoproteins, lipoproteins,
glycolipoproteins, lipids, fats, sterols, sugars, carbohydrates,
nucleic acid molecules, small organic molecules, or more complex
organic molecules. The target partner can also be molecular
complexes and inorganic molecules or ions. The target binding
partners may be intracellular target partners obtained from cells,
cytoplasm or matrix of cellular organelles, which have been
lysed.
The reaction conditions for immunoassays, hybridization reactions,
etc can be found in text books and laboratory handbooks. If a
plurality of analytes and reagents are used. It is most convenient
to use standardized conditions for the different reactants.
A binding assay records a result obtained from sample processing
and includes any assays comprising adsorption and desorption
reactions applying affinity capturing. Generally, a binding assay
determines the presence, amount, or activity of one or a plurality
of target binding partner in a sample. Adsorption includes binding,
coupling or capturing and is a characteristic step in the binding
assay and facilitates the purification and final separation and
detection of one or a plurality of target binding partners from a
sample.
The binding assay of the present invention comprises sequential
steps including adsorption and desorption reactions with
intermediate washing, which can be repeated with different reagents
or by introducing a new sample. In an integrated microfluidic chip
device of the present invention, the different steps are performed
sequentially to obtain a final result. When two tasks are performed
sequentially, the second task uses one or a plurality of products
of the first task. In the present invention the product means a
target binding partner in the sample that has been immobilized on a
magnetic microbead and purified, or concentrated in the first step,
or has became bound to a reagent which is also bound to said
magnetic microbead.
Target binding partners are immobilized on magnetic microbeads and
thereafter allowed to react with their counterparts to form binding
pair complexes or they are allowed to react with their
counterparts, which have been previously attached to magnetic
particles or are attachable to the magnetic beads. The target
binding partners and their counterparts as well as appropriate
affinity tags and detection labels are simultaneously allowed to
contact the magnetic microbeads, thereby the reactions between the
binding partners take place in solution and the binding pairs
formed are immobilized as complexes.
Without applying the method of the present invention about 5%, 10%,
20%, 30%, 40%, or 50% of the target partners are immobilized with
their binding pairs on the magnetic particle. By manipulating the
magnetic particles by forcing them through the microfluidic pillar
filter the formation of immobilized binding pairs may be increased
up to about 60%, 70%, 80%, 90%, or 100%
In the present invention immobilized means that something is
coupled, captured or bound to a solid support, the magnetic
microbead. A target binding partner and its counterpart may for
example be coupled to a magnetic microbead by specific or
nonspecific binding. The binding can be covalent or non-covalent,
reversible or irreversible, preferably affinity pairs, such as
biotin avidin and biotin streptavidin are used to facilitate
binding between on binding partner and the magnetic microbead.
In contrast to immobilized the term trapped means that a mechanical
barrier is used to prevent the magnetic microbead with the
immobilized targets and reagents from moving.
In the present invention separation means a process in which a
plurality of target partners or their binding pairs present in a
sample are spatially separated from one or more other target
partners using chromatographic equipment for separation, applying
capillary electrophoresis, gravity, mass flow, dielectrophoretic
forces, and electromagnetic forces.
A target binding partner is one of two different molecules having
an area on the surface or in a cavity in the three dimensional
structure of the molecule, which cavity specifically binds to and
is thereby defined as complementary with a particular spatial and
polar organization of the other molecule. A specific target partner
can be a member of an immunological pair such as antigen-antibody,
biotin-avidin or biotin streptavidin, ligand-receptor, nucleic acid
duplexes, DNA-DNA, DNA-RNA, RNA-RNA, and the like. It is to be
noted that the binding partners are soluble in a water-based
solution, but have affinity for each other and have affinity for
the magnetic microbeads or can be provided with a groups, which has
affinity for the microbeads or a member of an affinity pair
attached on the microbead.
A water-based solution is a biological sample solution, a
physiological buffer, biocompatible liquids used as hybridization
solutions, denaturating solution or for elution in the gel
electrophoresis. Laboratory handbooks provide a multitude of useful
water-based solutions. By changing temperature, ph conditions and
ingredients in said solutions it is possible to alternating
adsorption and desorption reactions on the magnetic microbeads or
beads.
Nucleic acid molecules are polynucleotide sequences. A nucleic acid
molecule can be DNA, RNA, or a combination of both. A nucleic acid
molecule can also include sugars other than ribose and deoxyribose
incorporated into the backbone. The backbone can be other than
those in DNA or RNA. Locked nucleosides form LNA and peptide
backbones form PNA and comprise nucleotide bases that are naturally
occurring or that do not occur in nature. A nucleic acid sequence
can have linkages other than phosphodiester linkages. A nucleic
acid sequence can be a peptide nucleic acid molecule, in which
nucleotide bases are linked to a peptide backbone. A nucleic acid
sequence can be of any length, and can be single-stranded,
double-stranded, or triple-stranded.
Standard binding assays include those that rely on nucleic acid
hybridization to detect specific nucleic acid sequences, those that
rely on antibody binding to entities, and those that rely on
ligands binding to receptors.
In a conventional binding assay, a detectable label is generally
needed in order to enable determination, measurement or recording
of the result. A detectable label is a compound or molecule that
can be detected or can generate a measurable signal. Useful labels
are fluorescence, radioactivity, color, or chemiluminescence.
Preferred are fluorescent labels, which are commercially available
and include Cy-5, phycoerythrin, phycocyanin, allophycocyanin,
FITC, rhodamine, or lanthanides; and by fluorescent proteins such
as green fluorescent protein (GFP). These and any other suitable
labels may be used in accordance with the present invention. The
reagent can be prelabeled, but methods exist by which the unlabeled
reactants may be labeled after the reaction. In some cases this is
the preferred method, by which steric hindrances caused by the
labels can be avoided.
The microchip device with the microfluidic channel system may be
used for performing transcript analysis by the aid of affinity
capturing (TRAC) and for determining the amounts of target
polynucleotide sequences and nucleotide variations therein, e.g.
from a cell lysate.
According to one aspect of the invention the microchip device may
be used in a binding assay, wherein first a buffer solution
comprising magnetic particles covered by counterparts, e.g. a
mixture of known antigens or antibodies, of the binding substance,
e.g. antibodies or antigens, respectively, is injected into the
tubular microfluidic channel system (100) and is transferred to the
a reaction chamber (101, 102) with microfluidic pillar filters or
grids (301, 302) by the stream of solution. A sample solution
containing a mixture of the binding partners, e.g. the respective
antibodies or antigens, is injected to the tubular microfluidic
channel and is mixed with its counterparts attached on the magnetic
microbeads. The inlets are closed by externally controlled
mechanical valves. The clustering magnetic microbeads may be
disintegrated by forcing them through the microfluidic pillar
filters to another reaction chamber by the aid of magnetic rods.
This transfer back and forth may be repeated one or more times.
Thereby a thorough mixing of the reagents is also achieved. After a
suitable time, which ensures a complete reaction between the
binding substance and its counterpart, the solution is removed
through one of the outlets, while the magnetic particles are
retained in one of the chambers behind the filter when the magnetic
forces or rods are switched off by raising the magnetic rod up. The
tubular microchannels are opened with external mechanical valves
and a stream of washing solution is injected through the tubular
microfluidic channel to the reaction chamber, wherein the magnetic
microbeads covered by the complexes of binding partners and their
counterparts are washed free from unbound sample and reagents by
forcing the microbead through the filters and by trapping them
during drainage of the solutions. This procedure may be repeated
one or more times and finally the binding substances are released
using, for example a buffer solution capable of releasing the
binding partner from its counterpart, which is retained in the
reaction chamber with the magnetic microbeads. The releasing buffer
solution preferably is a solution, which can be used for elution in
the subsequent capillary or gel electrophoresis, which separates
the binding substances, before recording their optical properties.
The magnetic particles with the captured counterparts of the
binding substances are retained and can after washing be reused by
adding another sample from which the same multi-analysis can be
performed.
According to a further aspect of the invention, the use of the
microchip is demonstrated as a method for quantifying expressed
target mRNA. In a still further exemplified aspect of the invention
the microchip device of the present invention is applied for
determining the amount of target polynucleotide sequences and
nucleotide variations therein.
A sample is any fluid from which components are to be separated or
analyzed. A sample can be from any source, such as an organism,
group of organisms from the same or different species, the cells of
which are subjected or have been subjected to lysis. It may be an
extract from the environment, as soil, food, buildings or any other
solid source. In a microfluidic system the sample should be in
liquid form as a solution or an extract, for example a liquid
extract of a soil or food sample, an extract of a throat or genital
swab, or an extract of a fecal sample. Blood samples are preferably
centrifuged, lysed, filtered, extracted, or otherwise treated blood
sample, including a blood samples to which one or more reagents
such as anticoagulants or stabilizers have been added. The sample
can be an unprocessed or a processed sample.
The processing of a sample starts with sample preparation, which
may include the disruption of a cell or tissue sample to release
the target partners or components to be determined. Sample
preparation may involve a crude separation or purification
including separation of polynucleotide sequences and proteins, but
a cell sample may be introduced directly into the microfluidic
channel system, wherein it subjected to lysis, or it may be
introduced after external lysis. The sample processing usually
includes separation of components of a sample, but in the present
invention the target partners or components of the sample are
processed together and the separation and identification of the
target partners is carried out the adsorption and desorption
reactions. The disruption may include lysis, denaturation rendering
for example double-stranded nucleic acid sequences or fragments
thereof single-stranded, chemical modification, or binding of
components to reagents. A processing step can act on one target
partner in the sample by releasing, exposing, modifying or generate
another type of component, e.g. the binding pair of target partner
that can be used in a further processing or analysis. The tasks
include measurement and calculation. For example, lysis of one or
more cells or tissues can be a first processing step to release
nucleic acids that can be separated in a further step task and
detected in a subsequent analysis step. Binding or coupling can be
a step in a processing task, where binding or coupling,
particularly the coupling of a target partner in a sample to its
binding pair present on a microbead facilitates the separation,
transportation, immobilization, isolation, focusing, concentration,
enrichment, structural alteration, or at least partial purification
of one or a plurality of target partners of a sample. In
conventional prior art methods mixing is a necessary task for
facilitating the binding, separation, transportation,
concentration, structural alteration, or purification of one or
more target partners in a sample. Mixing is a problem in a
microfluidic channel system, which does not allow introduction of
sufficiently effective forces. In the present invention a
sufficient mixing is provided by forcing magnetic microbeads
through the pillar filter by switching a magnetic rod on and
off.
The present invention relates to methods for performing binding
assays using magnetic microbeads. The target binding partner is a
component, in principle it can be any constituent in a water based
liquid sample, which has a specific affinity for and binds to
another component when contacted with its binding pair.
The method may be applied for PCR-cycles, which can be carried out
in the fluidic channel or in reaction chamber and for providing the
target polynucleotide sequences or the probe sequences with
detectable labels and for diminishing the background noise by
performing two subsequent PCR-cycles with a probe sequences having
two universal primers by initiating the PCR-cycle e with a sequence
provided with a detectable label complementary to one of the
universal primers and initiating a second PCR-cycle with another
sequence which is provided with a sequence complementary to the
other universal primer. Capturing the hybrid formed, which hybrids
are provided with an affinity tag and detectable label by
contacting the hybrids with magnetic microbeads, forcing the
magnetic microbeads through the microfluidic pillar filter and
keeping the microbeads behind a microfluidic pillar filter while
removing the redundant liquids, repeating the steps with washing
solutions and eluting the probe or target provided with a
detectable label from the hybrid in a small volume of elution
solution and leading said solution into the separation system and
for recording.
In the present invention, at least three main types of microfluidic
chip devices are disclosed. The three different types of microchip
devices include microchip devices with possibilities for carrying
out binding assays, binding assays with a polymerase chain reaction
(PCR chips); microchip devices with possibilities to carry out both
binding assays with PCR and capillary electrophoresis (CE) with a
straight CE channel or a serpentine CE channel. As a common feature
all three types of microchip devices have at least two different
fluidic couplings, including but not limited to side couplings and
liquid needles.
The use of the microfluidic chip device for performing a
miniaturized transcript analysis by aid of affinity capturing
(TRAC) assay is described below. Conventional TRAC assays are
described in the European Patent Nos. 1352097 and 1537238. One
object of a TRAC assays is to determine from a sample solution the
relative amounts of a plurality of expressed mRNA.
The method may comprise the following steps:
(a) contacting a liquid stream comprising a sample solution
containing a plurality of sample soluble target mRNA, poly(T)
probes with affinity tags, preferably biotin tags and a plurality
of stable single stranded probe sequences labeled with detectable
labels, preferably fluorophors and having sequences complementary
to the target mRNA, the relative amounts of which are to be
determined, and wherein each of the plurality of probe sequences
have sizes or masses which have distinct sizes, with magnetic
microbeads (401) by introducing said liquid stream into the
microfluidic channel system (100) comprising two reaction chambers
(101, 102) through connection (201) acting as an inlet and through
microfluidic pillar filter (301) to remove bubbles a liquid stream
and subsequently sealing fluidic connections (201, 202, and
203);
(b) allowing immobilization and hybridization reactions to take
place in favorable conditions for a time sufficient to provide
immobilized target mRNA-probe complexes on the magnetic microbeads
by transferring the magnetic microbeads back and for the through at
least one of the microfluidic pillar filters (301 or 302);
(c) trapping the magnetic microbeads with the immobilized
(captured) target mRNA-probe complexes (hybrids) on the
microfluidic pillar filter (302) by switching off the magnetic rod
(402) and removing the liquid stream through the liquid connection
(202) and closing connection (202);
(d) purifying the magnetic microbeads with the immobilized target
mRNA-probe complexes by introducing a new liquid stream containing
a washing solution favoring hybridization by switching on the
magnetic rod (402) and forcing the magnetic microbeads back and
forth through at least one of the microfluidic pillar filters (301,
302);
(e) trapping the magnetic microbeads with the immobilized target
mRNA-probe complexes on or behind the microfluidic pillar filter
(302) by switching off the magnetic rod (402) and removing the
liquid stream through the liquid connection (202) and closing
connection (202);
(f) releasing the probes from the target mRNA-probe complexes
immobilized on the magnetic microbeads by introducing a new liquid
stream containing a denaturating solution rendering the double
stranded complex single stranded and by switching on the magnetic
rod (402) and forcing the magnetic microbeads back and forth
through at least one of the microfluidic pillar filters (301, 302)
allowing the denaturation take place for a time sufficient to
release the probes;
(g) trapping the magnetic microbeads with the immobilized target
mRNA on the microfluidic pillar filter (302) by switching off the
magnetic rod (402) and introducing the liquid stream containing the
probes into a microfluidic channel outlet for optional
amplification and/or concentration before allowing the probes to
enter the separation equipment and performing a capillary
electrophoresis for separating and discriminating the plurality of
probes from each other and graphically recording the intensity of
the detectable label (fluorescence) of each of the probes and by
using software-associated automatic or semiautomatic instruments
calculating the amount of the probes from the graphically recorded
peaks (202) which corresponds to the relative amount of target mRNA
present in the sample solution.
By adding a further step to the method described above relative
amounts of expressed mRNA and nucleotide variations therein can be
determined. The method is a miniaturized version of the method
described in the International Patent Application No. WO
2008/102057 (PCT/FI2008/050074), which is incorporated herein by
reference in its entirety.
In the additional step, the oligonucleotide probes which are
immobilized and purified in step (d) are elongated in their
3'-terminal end using the 5'-terminal end of the target mRNA as a
template; by introducing after step (e) through the liquid
connection (201) and the microfluidic pillar (301) a buffer
solution comprising an enzyme, such as a polymerase or reverse
transcriptase, which in the presence of at least one
deoxynucleotide, such as dTTP, dATP, dCTP or dGTP or at least one
dideoxynucleotide such as ddTTP, ddATP, ddCTP or ddGTP is capable
of elongating the probe using the target mRNA as a probe. By
switching on the magnetic rod (402) and forcing the magnetic
microbeads with purified immobilized target mRNA-probe complexes
through the microfluidic pillar filter (302), the elongation
reaction is allowed to take place for a sufficient time and in
conditions favouring elongation reaction. After trapping and
purifying the magnetic microbeads, the probes with or without
elongations are released, separated and recorded. From the peaks in
the graphically recorded results and using appropriate controls the
relative amounts of the probes with or without elongations can be
calculated and the amounts of the complementary target mRNA and
nucleotide variations in said mRNA, which have hybridized with the
original probes, can be evaluated.
As said above the released probes may be amplified in the
microfluidic chip device before they are separated by e.g.
capillary electrophoresis and the intensity of the label is
recorded.
According to another aspect of the invention, the microfluidic chip
device of the present invention may be used in methods for carrying
out a PCR reaction. This PCR-reaction may be carried out before
transferring the probe polynucleotides, which have hybridized to
the analyte sequences and which have been purified when captured on
the solid support, and thereby separated from unreacted sequences
in the sample.
The magnetic rod is let down to the reaction chamber (101) and a
solution containing magnetic microbead is fed in from the liquid
connection (201). The magnetic microbeads are washed and a DNA
sample is added from the liquid connection (201). The magnetic
microbeads are moved from one chamber to another by moving the
magnetic rod from the reaction chamber (102) to the bubble filter
chamber (101). A PCR amplification mixture is added from liquid
connection (201) and the magnetic microbeads are moved from the
bubble filter chamber (101) to the reaction chamber (102) and
channel, wherein the PCR reaction takes place and moves them to the
bubble filter chamber (101). The solution is fed or added from
liquid connection (201) and the magnetic microbeads are moved by
the magnetic rod (402) from bubble filter chamber to reaction
chamber (102) and the channel (103). Thereafter, the DNA is eluted
from the magnetic microbeads, which are moved by the magnetic rod
to bubble filter chamber (101). An optional electrical
pre-concentration is carried out with the high voltage electrodes
(505). A separation electrolyte is transferred to CE/ITP channel
(600). The sample is injection from inlet (203) to CE/ITP: 2 (600).
An optional ITP pre-concentration is carried out and the DNA
identification is carried out with CE separation. The DNA
identification in ITP/CE channel may be carried out with at least
five different DNA identification procedures in the ITP/CE
channel.
1. The identification is carried out by concentration of the sample
with ITP before CE separation. The ITP is carried out in a side
channel of the main CE channel. The CE separation is carried out
after the ITP concentration.
2. Simultaneously pressure/electrical injection from PCR cavity.
Concentrated sample between parallel conductivity electrodes in an
injection loop present in the microfluidic chip device straight or
in a loop channel in the microfluidic chip device shown in FIGS.
5A-5H. The CE separation is carried out after the sample
injection.
3. The sample injection toward the gel solution interface is
carried out in sample loop (600) in the microfluidic chip devices
shown in FIGS. 5A-5H. The CE separation is carried out in a buffer
solution.
4. Gel electrophoresis is carried out with ITP concentration. The
whole CE channel is filled with gel solution. The CE separation is
carried out in gel solution.
5. Sample injection is carried out in double T injection
microfluidic chip device shown in FIGS. 5E-5H. The CE separation is
carried out after sample injection.
It will, of course, be appreciated that the above description has
been given by way of example only and that modifications in detail
may be made within the scope of the present invention.
The invention is capable of considerable modification, alteration,
and equivalents in form and function, as will occur to those
ordinarily skilled in the pertinent arts having the benefit of this
disclosure.
While the present invention has been described for what are
presently considered the preferred embodiments, the invention is
not so limited. To the contrary, the invention is intended to cover
various modifications and equivalent arrangements included within
the spirit and scope of the detailed description provided
above.
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